A method and apparatus for testing spark plugs and ignition coils. An apparatus includes a power supply for supplying power to an ignition coil to generate a spark across a spark plug. A capture circuit captures an energy signal reflected from the ignition coil in response to the spark. A comparator circuit compares the captured energy signal to a predetermined signal. A method includes the steps of supplying power to an ignition coil to generate a spark across a spark plug, capturing an energy signal reflected from the ignition coil in response to the spark and comparing the captured energy signal to a predetermined signal. The predetermined signal represents one of a distinct group of reflected energy signals which indicate various defects in the coil or plug. Preferably, a match between the captured energy signal and the predetermined signal is used to indicate to the user a defective coil or plug.
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30. In an engine assembly line, an apparatus for cold motor testing an engine having at least one ignition coil and at least one spark plug, the improvement comprising:
a power supply for supplying power to the ignition coil to generate a spark across the spark plug; at least one capture circuit positioned between the power supply and each ignition coil for capturing an energy signal reflected from the ignition coil in response to said spark generation; and a comparator circuit for comparing said captured energy signal to a predetermined signal.
32. In an apparatus for testing an ignition coil connected to a spark plug, the improvement comprising:
a power supply for supplying power to the ignition coil to generate a spark across the spark plug wherein the ignition coil and the spark are installed in an engine having a separate ignition coil and spark plug for each engine cylinder; a capture circuit for capturing an energy signal reflected from the ignition coil in response to said spark generation; and a comparator circuit for comparing said captured energy signal to a predetermined signal.
19. A method for testing an ignition coil connected to a spark plug, the ignition coil having first and second windings, the second winding in electrical communication with the spark plug defining a secondary side circuit, the method comprising the steps of:
supplying power to the first winding of ignition coil defining a primary side circuit to generate a spark across the spark plug; capturing an energy signal reflected from only the first winding of the ignition coil in response to the spark generation; and comparing the captured energy signal to a predetermined signal to detect a defect in the secondary side circuit.
28. A method for testing an ignition coil connected to a spark plug, comprising the steps of:
supplying power to the ignition coil to generate a spark across the spark plug, wherein an insulation boot assembly including a contact spring is connected between the ignition coil and the spark plug; capturing an energy signal reflected from the ignition coil in response to the spark generation; and comparing the captured energy signal to a predetermined signal representing a reflected energy signal produced by an ignition coil connected to a spark plug with an insulation boot assembly having an electrically open contact spring.
15. An apparatus for testing an ignition coil connected to a spark plug, comprising:
a power supply for supplying power to the ignition coil to generate a spark across the spark plug; a capture circuit for capturing an energy signal reflected from the ignition coil in response to said spark generation; and a comparator circuit for comparing said captured energy signal to a predetermined signal, wherein an output of the comparator circuit identifies one of a spark plug having a cracked insulator, a spark plug having an electrode spacing approximately equal to or less than 0.050 inches, a spark plug having an electrically shorted pair of electrodes, an electrically open spark plug, and an electrically open ignition coil.
17. An apparatus for testing an ignition coil connected to a spark plug wherein an insulation boot assembly including a contact spring is connected between the ignition coil and the spark plug, the apparatus comprising:
a power supply for supplying power to the ignition coil to generate a spark across the spark plug; a capture circuit for capturing an energy signal reflected from the ignition coil in response to said spark generation; and a comparator circuit for comparing said captured energy signal to a predetermined signal, said predetermined signal representing a reflected energy signal produced by an ignition coil connected to a spark plug with an insulation boot assembly having an electrically open contact spring.
1. An apparatus for testing at least one ignition coil and at least one spark plug in a spark-ignition engine where said engine has one of a single ignition coil with a plurality of connected spark plugs and a plurality of ignition coils with a single spark plug per coil, the apparatus comprising:
a power supply for supplying power to each ignition coil to generate a spark across each associated spark plug; at least one capture circuit for capturing an energy signal reflected from each ignition coil in response to said spark generation, each capture circuit positioned between the power supply and each ignition coil for a particular engine to be tested; and a comparator circuit for comparing said captured energy signal to a predetermined signal.
29. method for testing an ignition coil connected to a spark plug wherein the ignition coil and the spark plug are installed in an engine having a plurality of cylinders, each cylinder having a separate ignition coil and spark plug, comprising the steps of:
supplying power to the ignition coil to generate a spark across the spark plug, wherein a separate supply voltage wire is routed between a power supply and the separate ignition coil of each cylinder; capturing an energy signal reflected from the ignition coil in response to the spark generation; and comparing the captured energy signal to a predetermined signal representing a reflected energy signal produced by an ignition coil connected to a power supply with a misrouted supply voltage wire.
31. An apparatus for testing an ignition coil connected to a spark plug, the ignition coil having first and second windings, the second winding in electrical communication with the spark plug defining a secondary side circuit, the apparatus comprising:
a power supply connectable to the first winding of the ignition coil defining a primary side circuit for supplying power to the first winding to generate a spark across the spark plug; a capture circuit for capturing an energy signal reflected from the first winding of the ignition coil in response to said spark generation; and a comparator circuit for comparing said captured energy signal to a predetermined signal and generating an output in response to a match between said captured energy signal and said predetermined signal indicating a defect in the secondary side circuit.
18. An apparatus for testing a set of ignition coils and spark plugs installed in a spark-ignition engine, each ignition coil having first and second windings, the second winding in electrical communication with each associated spark plug, the apparatus comprising:
a power supply connectable to the first winding of each ignition coil for supplying power in a predetermined cycle to the first winding of each ignition coil to generate a spark across each spark plug; a signal isolation and conditioning circuit for capturing and conditioning each analog voltage waveform signal reflected from only the first winding of each ignition coil in response to each spark generation; a digital scope circuit for digitizing each of said captured analog voltage waveform signals; and a central processor for comparing each of said digital signals to a plurality of predetermined signals to detect one of a defective ignition coil and a defective spark plug.
16. An apparatus for testing an ignition coil connected to a spark plug wherein the ignition coil and the spark plug are installed in an engine having a separate ignition coil and spark plug for each engine cylinder, the apparatus comprising:
a power supply for supplying power to the ignition coil to generate a spark across the spark plug; a capture circuit for capturing an energy signal reflected from the ignition coil in response to said spark generation; and a comparator circuit for comparing said captured energy signal to a predetermined signal; and wherein the engine includes a plurality of cylinders each having a separate coil and spark plug and wherein said power supply includes an ignition system circuit for supplying power to each ignition coil in a predetermined cycle and wherein a separate supply voltage wire is routed between said power supply and each ignition coil and wherein said predetermined signal represents a reflected energy signal produced by an ignition coil connected to a power supply with a misrouted supply voltage wire.
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This application claims the benefit of U.S. Provisional Application No. 60/080,221, filed Mar. 31, 1998.
The subject invention relates to an apparatus and method for testing an ignition coil and a spark plug and, more particularly, to an apparatus and method capable of identifying defects in an ignition coil and a spark plug connected in a "coil on plug" design.
Most conventional spark-ignition engines include a single ignition coil wired to several spark plugs for initiating fuel combustion in each engine cylinder. To ensure quality, these engines are typically cold motor tested for defects prior to shipment to a vehicle assembly plant. During the cold motor testing, each engine is mechanically cranked by an external testing mechanism through at least one complete engine cycle. Thus, there is no combustion of fuel during the cold motor testing.
To detect ignition coil and spark plug defects, conventional engine testing methods have monitored an electrical signal transmitted from a secondary side of the ignition coil to each spark plug during each spark generation. However, the recent development of a new ignition coil and spark plug packaging arrangement, commonly referred to as a "coil on plug" design, has rendered such prior art testing methods obsolete.
Unlike conventional designs, the "coil on plug" arrangement provides one ignition coil and one spark plug for each engine cylinder. The "coil on plug" design additionally includes a boot or sleeve which extends from the secondary side of the ignition coil to the middle of the spark plug. Thus, the boot insulates the entire length of an electrical transmission wire connected between the ignition coil and the spark plug. As a result, access to the aforementioned electrical signal is not available in the "coil on plug" design. Accordingly, it would be desirable to provide an apparatus and method for testing an ignition coil and a spark plug connected in a "coil on plug" design.
In a disclosed embodiment of this invention, an apparatus tests an ignition coil and a spark plug for defects. The apparatus includes a power supply for supplying power to the ignition coil to generate a spark across the spark plug. A capture circuit captures an energy signal reflected from the ignition coil in response to the spark generation. A comparator circuit compares the captured energy signal to a predetermined signal.
The ignition coil includes a first winding in electrical communication with the power supply and a second winding in electrical communication with the spark plug. Accordingly, the energy signal is reflected from the first winding of the ignition coil in response to the spark generation.
The predetermined signal represents one of a group of distinct reflected energy signals which indicate various defects in an ignition coil or spark plug. In a preferred embodiment, the comparator circuit generates an output in response to a match between the captured energy signal and the predetermined signal to indicate a defective ignition coil or spark plug.
The present invention also provides a method for testing an ignition coil and a spark plug for defects. The method includes the steps of: supplying power to the ignition coil to generate a spark across the spark plug; capturing an energy signal reflected from the ignition coil in response to the spark generation; and comparing the captured energy signal to a predetermined signal. Preferably, the method further includes the step of generating an output in response to a match between the captured energy signal and the predetermined signal to indicate a defective ignition coil or spark plug.
The present invention provides an apparatus and method capable of testing an ignition coil and a spark plug connected in a "coil on plug" design for various types of defects. The present invention is also capable of disclosing which specific type of defect was detected.
Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
Referring now to the Figures, wherein like numerals indicate like or corresponding parts throughout the several views,
The ignition coil 10 functions as both an energy-storage device and a transformer. The ignition coil 10 includes a first electrical winding 16 and a second electrical winding 18 disposed within a housing 20. In
To transmit the ignition voltage, the insulation boot assembly 12 includes a transmission wire 24 and a contact spring 26 disposed within an insulation sleeve 28. In
The upper body portion 30 of the spark plug 14 is commonly referred to as the insulator. A lower body portion 32 of the spark plug 14 is commonly referred to as the shell. Typically, the insulator 30 is made from a ceramic material and the shell 32 is made from a metal material. A high voltage connector 34 is disposed at the distal end of the insulator 30. A pair of spaced electrodes 36 and 38 are disposed at the opposing end of the spark plug 14. The high voltage connector 34 is shaped to form an electrical connection with the contact spring 26 within the insulation boot assembly 12. The electrodes 36 and 38 are specifically gaped or spaced so as to produce an electrical arc when the ignition voltage is supplied to the spark plug 14.
The apparatus 50 includes a power supply 54 for supplying power to the ignition coil 10 to generate a spark across the spark plug 14. A capture circuit 56 captures an energy signal reflected from the ignition coil 10 in response to the spark generation. A comparator circuit 58 compares the captured energy signal to a predetermined signal. Preferably, the comparator circuit 58 also generates an output in response to a match between the captured energy signal and the predetermined signal.
As shown in
The predetermined signal may be selected from one of a distinct group of reflected energy signals that indicate a defective ignition coil, a defective insulation boot assembly, a defective spark plug or a misrouted supply voltage wire. Specifically, the predetermined signal may be selected to identify the following defects: an electrically open ignition coil; an insulation boot assembly having an electrically open contact spring; a spark plug having a cracked insulator; a spark plug having an electrically shorted pair of electrodes; a spark plug having an electrode gap approximately equal to or less than 0.050 inches; an electrically open spark plug; and an ignition coil connected to a misrouted supply voltage wire. A misrouted supply voltage wire includes a pair of ignition coils connected to a pair of crossed or swapped supply voltage wires. Alternatively, the predetermined signal may be selected to represent a reflected energy signal produced by a properly wired, non-defective "coil on plug" assembly.
In a preferred embodiment, the power supply 54 includes an ignition system circuit 60 for supplying power to each ignition coil 10 in the engine 52 in a predetermined cycle. Typically, the predetermined cycle is set to replicate the spark plug timing and firing sequence specifically designed for the engine to be tested.
The capture circuit 56 includes a signal isolation and conditioning circuit 62 and a digital scope board 64. The signal isolation and conditioning circuit 62 performs several functions. During the test procedure, the signal circuit 62 captures an analog voltage signal reflected from the first winding 16 of one of the ignition coils 10 and identifies from which specific ignition coil 10 the signal was reflected. The signal circuit 62 conditions the captured analog voltage signal by transforming the captured signal from a 0-350 volt peak to peak signal to a 0-10 volt peak-to-peak signal. After the captured signal is conditioned, the signal circuit 62 transmits the conditioned 0-10 volt signal to the digital scope board 64. As an additional feature, the signal circuit 62 isolates the initial 0-350 volt signal from the digital scope board 64 and, thereby, provides a protection against a short to ground condition. A device which meets the functional requirements of the signal isolation and conditioning circuit 62 as described above is manufactured by Freese Enterprises Incorporated, located in Plymouth, Mich., identified as "FEI Signal Isolation and Commutation MODEL".
The digital scope board 64 receives the conditioned analog voltage signal from the signal circuit 62, converts the analog signal to a digital voltage waveform signal, and transmits the digital waveform signal to the comparator circuit 58. To receive or capture the entire analog voltage signal from the signal circuit 62, the digital scope board 64 samples the analog voltage signal at a sampling rate of approximately 10 Ms/s (million samples/second) or faster. A device which meets the functional requirements of the digital scope board 64 as described above is manufactured by PC Instruments, located in Akron, Ohio, identified as "443 Scopeboard".
The comparator circuit 58 includes a central processor 66 for storing the predetermined signals (see
The preselected, indicative portion of each predetermined "defective" signal (see
The preselected, indicative portion of the electrically shorted spark plug signal 78 is the duration of the ignition voltage portion generally indicated by 92 in
The preselected, indicative portion of the remaining five predetermined "defective" signals (i.e. the electrically open contact spring signal 74, the cracked spark plug insulator signal 76, the insufficiently gaped spark plug signal 80, the electrically open spark plug signal 82, and the misrouted supply voltage wire signal 84) is a specific area underneath each "defective" signal generally indicated by 94 in
The apparatus 50 is programmed to capture a reflected energy signal from each "coil on plug" assembly 15 during at least one complete engine cycle and then test each "coil on plug" assembly 15 for the various types of defects in a predetermined order.
The present invention also provides a method for testing an ignition coil connected to a spark plug. The method includes the steps of: supplying power to the ignition coil to generate a spark across the spark plug; capturing an energy signal reflected from the ignition coil in response to the spark generation; and comparing the captured energy signal to a predetermined signal. Preferably, the method further includes the step of generating an output in response to a match between the captured energy signal and the predetermined signal to indicate a defective ignition coil or a defective spark plug.
The predetermined signal may be selected from one of a distinct group of reflected energy signals that indicate a defective ignition coil, a defective insulation boot assembly, a defective spark plug, or a misrouted supply voltage wire. Specifically, the predetermined signal may be selected to identify the following defects: an electrically open ignition coil; an insulation boot assembly having an electrically open contact spring; a spark plug having a cracked insulator; a spark plug having an electrically shorted pair of electrodes; a spark plug having an electrode gap approximately equal to or less than 0.050 inches; an electrically open spark plug; and an ignition coil connected to a misrouted supply voltage wire. Alternatively, the predetermined signal may be selected to represent a reflected energy signal produced by a properly wired, non-defective "coil on plug" assembly.
Although the apparatus and method are suited primarily for testing an ignition coil and a spark plug connected in a "coil on plug" design, one of ordinary skill in the art will recognize that the present invention may also be used to test for defects in an electrical spark-ignition system which includes a single ignition coil wired to two or more spark plugs. One of ordinary skill in the art will further recognize that the present invention is capable of detecting defects in an insulation boot assembly connected between an ignition coil and a spark plug and is capable of detecting a misrouted supply voltage wire connected between a power supply and an ignition coil.
To determine the reflected energy signal of a defective "coil on plug" assembly (see graphs in FIGS. 3B-3H), an engine including a "coil on plug" assembly having a single known defective component was cold motored or rotated and the reflected energy generated by the spark plug generation was measured on the primary side of the ignition coil. All data was collected with the coil and plug being fired for the first time as would be the case in the normal assembly process. With such data, the apparatus of the present invention can compare an actual reflected energy signal with the "defective" reflected energy signals to detect secondary ignition assembly defects.
The present invention provides an apparatus and method capable of testing a "coil on plug" assembly, and the respective supply voltage wiring, for various types of defects. Further, the present invention is also capable of disclosing which specific type of defect was detected.
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